Visible Light Transmittance (VLT)
Last Updated: July 30, 2024
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Visible Light Transmittance (VLT)
Visible Light Transmittance (VLT)
Share via E-mailVisible Light Transmittance (VLT) is a measure of how much visible light passes through a window or door glass. It is expressed as a percentage, representing the amount of visible light transmitted through the glass relative to the total visible light that hits the surface. A higher VLT percentage means more visible light is transmitted, while a lower VLT percentage means less visible light is transmitted.
Factors Affecting Visible Light Transmittance
- Glass Coatings: Cardinal’s LoĒ™ coatings and other surface treatments can reduce the VLT by reflecting and absorbing some of the visible light.
- Tint: Tinted glass can reduce VLT by absorbing or reflecting visible light.
- Glass Thickness: Thicker glass can have a slightly lower VLT than thinner glass due to increased absorption of visible light.
Importance of Visible Light Transmittance for Occupants
Natural Lighting: Glass with high visible transmittance allow more natural light into a building, reducing the need for artificial lighting and improving indoor ambience.
Passive Solar Gains in Cold Climates: By increased passive solar heat gain, some high VLT glass can aid in keeping the house warm in cold climates.
Daylighting: Glass with high visible light is essential for effective daylighting, a building design strategy that optimizes natural light to enhance indoor lighting quality and reduce energy usage.
Visibility: Glass with high visible transmittance provide clear views of the outdoors, enhancing the connection between indoor and outdoor spaces.
Glare Control: For locations with intense, direct sunlight, glass coatings with low visible transmittance like LoĒ³-340 and LoĒ²-240 glass can help control glare by reducing the amount of visible light transmitted, improving visual comfort.
